The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with dis-closures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Multicast services are becoming more and more popular with the development of cellular wireless networks (e.g. LTE networks), where data is transmitted to multiple recipients by eNB. An interesting multicast retransmission solution is in-band cooperative retransmission where one of the users who have already successfully received a packet is responsible for retransmitting the packet to users who have reported a negative acknowledgement (NACK) before. Thus the recipients in a multicast service may form a cluster to help each other in service data receiving.